Flotation apparatus



Oct. 30, 1951 W; A, WASLEY ET AL 2,573521 FLOTATION APPARATUS Patented Oct; 30, 1 951` UN l TED STATES y i i f FLoTAToN APPARATUS William Arthur wasey, Cana-noa, Marisa', 'ana John'Clement Maclntosh, Bisbee, Ariz', assignors to The'Cananea `Consolidated Copper Company S. A., a Mexican corporation vA'p'plicftov' October 7, 1947, Serial No. '778,436H

2 Clams'.

This invention relates to flotation apparatus, and is particularly concerned with the provision` of improvements in 'fiotation machines having submerged air pumps (impellers) driven by a vertical shaft that Vextends downwardly from above the normal level of an ore pulp in the machine. The invention is especially adapted for use in connection With fiotation machines of the Fagergren type. The principal feature of the present invention is the provision of a supplementary air screw com''prisingv a plurality of vanes projecting laterall'y fr'om the vertical air pump (or impeller) shaft adjacent the normal level of the ore pulp in the apparatus. -The vanes are pitched at an angle to the vertical so as to cause them to force air downwardly when the shaft is rotated in its normal operating direction.

A typical Fagergren-ty'pe flotation machine o-f the character to which the invention may be applied with advantage (such, for example, as is shown and described in Taggart's Handbl'ook of Mineral Dressing (1945 edition), section 12, pages 66 and 67) comprises a long trough-like chamber divided by transverse partitions into a plurality of cells. Each cell is provided with an air pu-mp for aerating the pulp comprising a substantially vertical rotatable impeller shaft, With an impeller mounted on the shaft at its lower end beneath the normal level of pulp in the' cell. A housing surrounds the impeller and shaft, and a splash cone generally i's provided inside the housing adjacent the normal level of the pulp in Vthe cell.

In apparatus of this' charact'er, the inventioii provides the improvement comprising a plurality of vanes pro-jecting laterally from the impeller shaft adjacent the normal level of the pulp, said vanes being pitched at such an angle 4.to the vertical as to force air downwardly toward the impeller during rotation of the impeller shaft in its normal Operating direction. The vanes may be permanently mounted on a collar having the proper inside diameter to slide-fit on the impeller shaft. The collar then may be provided with a set screw for clamping it and the vanes at a desired position on the shaft. The splash cone tself advantageously is formed with a substantially vertical cylindrical portion at its'lower' end; which surrounds but is spaced from the impeller shaft adjacent the normal level of the pulp. The vanes, in such case, are secured to the impeller shaft inside thiscylindrical lower extension of the splash cone. y y '1 -The vanes referred to 'serve a dual purpose:

They increase the amount' of air -whichithe 'fair' punf'ip impeller 'delversadahe'ore pulp ;.f and theyf.

prevent Vac(lumulatio of oro' pulp' mud 'in 'the' splash c-o'ne around the vijfpee'f shaft, th'r'eby insuring an open passageffor air from the 'atmose" phere to the impeller. A preferred enib'odiment of the inventioni'is; shown-in'the ac'companying' ''drawiig`s, in which Fig. l showsin per'sp'ective (parts 'being brcrkenv away) aV Fa'ge'rgren-type 'flotation' machine equipped inaccordance with the presentl inven=- Fig. 2' isa plan of the air's'jcrew assen'-bly'of'cii lar and vanes'shown-inFigrl; and Fig. 3f is an-elevation of the air'fscrew assembly showni'i'n '1'i g.w2.'v y

The flotation'maehine-shown in vFig. 1 comepris-es a long trouvgh-like chamber l having aliat' bot-tom 2, and side vwalls each having a lower portion V3 which slopes o-iitwardly from the-bottom and 'anupper* portion 4- which issubstantially vertical. The cha-mber divided bya series of trams-verso partitions 5 into af-plurality of individual cells (only two such cells are shownin' full, in Fig. l, but ordinarily the chainb'er fwill be long enough to contain five or'six similar' cells). v Y

A feed box G' i'sprovided -at one end of the trough-like chainber' I.- The erid wall 'l Vof the chamber which separats the feed box-46 fr'or'n-v the Chamber itself is'V formed With an -operi-i'g 8 near its bottom, so that an aqueoi's ore pulp' intro'duced into the feed .boi may enter and-'now length-wise through the Chamber. Opening's V9 in the transverse partitions 5 enablev the oro pulp to flow lengthwise from the feed box -serially through the several cells Vto a tailing dis'char'ge box ll) at the .opposite end of the Chamber. A vertical impeller shaft .ll is mounted sube' stantially centrally in each cell, in 'b'ea'rings 12'v Supported on vertical and Vh'orizontal frame mem-z bers |3 and 14. The impeller shafts are rotated in their bearings at fairly high speed by' 'a motor' l-5 connected by V--belts' [6 to pul'leys ll keye-d to the upper ends of the shaft's. r An impeller' |8 is'mounted' at the lower endof each shaft beneath the normal'levelzof the .ore'

pulp in the cell. The impeller comprises fan; like b'lades' I 9 set aty an'angle3 such as to force' air downwardly into' the orfe pulp when the' impeller shaft is 'rotated its* normal Operating dire'ci-v tion (clo'ckwise', as indicated'by the arrow, in the apparatus' shown-in' Fig.- 1')'. alsc'conr''oris'esa' squirrel cago of vertical rbars 20 which ret'a'te Withiflltheblades |-9` The':-:ir`n:- pelleriiarid'impeller s'h'aft aresurrouded-'by a.cy;-:V lindrical husing 2tl the upp'er portion 22 -:.'of.-

The impeller through the apparatus from cell to cell. These baifles, which serve to prevent rotary motion of the pulp in each cell, are not a part of Fagergrentype flotation machines as heretofore known. They form the subject matter claimed in our copending application Serial No.I 778,006,'fi1ed October 4, 1947, and are more fully described therein.

In the operation of the apparatus thus far desituated about at the normal level of pulp i tli cell, and the air screw assembly of collar 21 and vanes 26 is mounted inside it. The inside diameter of the downward extension 31 of the splash cone should be only slightly greater than the diameter of the circular path described by the outer edges of the vanes as they rotate with the impeller shaft. i

While splash cones geerally have been found necessary in flotation machines of the type described to minimize recirculation of splashed ore pulp and froth, they have often been found to provide a focal point for the accumulation of ore pulp mud. An accumulation of mud in the splash cone reduces the cross-sectional area of the passage through the cone through which air must scribed, an ore pulp to which suitable flotation i,

reagents have been added is introduced into the feed box 6 and flows lengthwise through the chamber i from cell'to cell. The impellershafts'* are rotated at a fairly high speed by the motor 5, so that the impeller blades IS suck air downwardly about the impeller shaft and deliver it radially outwardly through the rotating Vsquirrel cage bars and the stationary housing bars 23 into the body of the pulp. The air bubbles form a froth in the pulp, whichV rises 'to the surface carrying the mineral valuesY of the ore with it and overfiows into collecting launders 25 arranged alongside the upper edges of the vertical Vside members 4. The

gangue component of the ore does 'not fioat, `but flows with the-main body of the pulp to the tailing dischargebox 0, through which it is withdrawn.

It is, of course, important that an adequate amount of air be delivered to the pulp to insure formation of a large volume of froth. Otherwise deficient recovery of the mmcral values in the concentrate may result. In accordance with the invention, the delivery of an adequate Volume of air is insured by the provision of a plurality of vanes 26 secured to the impeller shaft H about at the normal surface level of the pulp in the cell. The vanes are pitched at such' an angle to the vertical that when the impeller shaft rotates in its normal Operating direction, they serve as fan or air screw blades to force air downwardly to the impeller. i i

The vanes can be welded or otherwise fastened directly to the impeller shaft J I, but preferably they are mounted on a collar 21, as by being welded thereto. The assembly of collar andvanes is'shown on an enlarged scale in Figs. 2 and 3. The internal diameter of the collar is just enough larger than the diameter of the shaft to slidefit easily therein. The collar is formed with threaded radial holes 28 to receive set screws 29 by which the collar may be clamped at a chosen position on the impeller shaft.

It is customary to provide Fagergren type flotation machines with a splash cone 30. The purpose of this cone is to prevent ore pulp splashed by the rotating impeller from being recirculated thereby. It is of course recognized that to whatever extent the impeller serves merely to recirculate splashed ore pulp, its capacity to'force air into the pulp is correspondingly diminished. In

` apparatus constructed in accordance with the inpass from the atmosphere to the impeller. An accumulation of mud therefore reduces the rate at which the impeller can deliver air to the pulp. We have found that the above-described air screw is extremely efficient in preventing any accumulation of ore pulp mud in the splash cone,

begin to accumulate in the opening of the cone,`

it isscraped ofi by the radially extending rotating vanes of the air screw.

It is apparent from the foregoing that the air screw vanes 26, rotating with the impeller shaft ll, insure delivery of an adequate Volume of air to the pulp in two ways: first, by keeping the air passage through the splash cone free from any accumulation of ore pulp mud; and, second, by positively forcing air downwardly toward the impeller. i

Tests have shown that the increased aeration of an ore pulp achieved by equipping Fagergrentype flotation machines with air screws of the character described results in improved recovery of mineral values in the concentrate, and reduced losses of the desired mineral values in the tailing. In a comparative test of Fagergren-type machines treating a pulp of sulphidic copper ore, in which some of the machines were equipped with airscrews of the character described and with baflies 24, and in which the other machines were not so equipped, it was found that the copper content of the tailings from the machines not equipped in accordance with the invention averaged, over a considerable period of time, about 20% higher than the copper content of the tailings from the machines that were equipped in accordance with the invention.

In addition to leading to improved flotation concentrate recovery of mineral values, the air screws of the invention also reduce the difiiculty of keeping the machines in good Operating con-.K dition, by reducing the frequency With which it is necessary to clean mud from the splash cone and elsewhere in the immediate vicinity of the impeller shaft.

We claim: y

1. In a flotation apparatus comprising a cell adapted to contain ore pulp and having therein means for aerating the pulp comprising A.a substantially vertical rotatable impeller shaft,. an aerating Vimpeller mounted fon the s haft atnthe lowerendV thereof beneaththe normal level of pulp inthe Acell, ..a housing surrounding; the

peller shaft, said housing being continuous and imperforate from the aerating impeller upwardly to above the level of the pulp thereby defining an enclosed air admission space about the impeller shaft above said impeller, and a splash cone inside the housing adjacent the normal level of the pulp, said splash cone having its apex cut away to form a circular opening through which the impeller shaft passes, the improvement comprising a plurality of vanes pitched at an angle to the vertical and projecting laterally from the impeller shaft in the enclosed air admission space directly above the aerating impeller, said vanes being positioned directly in the circular opening of the splash cone and extending radially from the shaft almost to the inner edge of the splash cone defining said circular opening, the pitch of said vanes being such that during normal rotation of the impeller shaft the vanes force air downwardly through the opening of the splash cone toward the impeller and the radial extension of the vanes beingsuch that accumulation of ore pulp mud in the opening of the splash cone is prevented by the mechanical scraping action of the rotating vanes.

2. In flotation apparatus comprising a cell adapted to contain a body of ore pulp and having therein means for aerating pulp comprising a substantially vertical rotatable impeller shaft, an aerating impeller mounted on the shaft at the lower end thereof beneath the normal level of pulp in the cell, and a housing surrounding the impeller and shaft, said housing being continuous and imperforate from the aerating impeller upwardy to above the eve of the pulp thereby defining an enclosed air admission space about the impeller shaft above said impeller, the improvement comprising a splashcone inside the housing above the impeller and terminating at its lower end in a substantially vertical cylindrical portion concentrically surrounding the impeller shaft adjacent the normal level of the pulp' but spaced from said shaft to form an annular air passageway around said shaft, and a plurality of vanes secured to the shaft adjacent the normal pulp level inside said cylindrical portion of the splash cone said vanes being pitched at an angle to the vertical and projecting radially from the impeller shaft almost to the inner surface of said cylindrical portion, the pitch of the vanes being such that during normal rotation of the impeller shaft the vanes force air downwardly through the cylindrical portion of the splash cone toward the aerating impeller and the radial extension of the vanes being sufficient to prevent accumi'lation of ore pulp mud in said cylindrical portion by mechanical scraping action When said shaft is rotated.

WILLIAM ARTHUR WASLEY.

JOHN CLEMENT MACINTOSH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STA'I'ES PATENTS Number Name Date 961,802 Russell June 21, 1910 2,294,827 Booth Sept. 1, 1942' 2.433,592 Booth Dec. 30, 1947 FOREIGN PATENTS Number Country Date 556,090 Great Britain Sept. 20, 1943 762,263 France v Jan. 18, 1934 505,793 Germany Aug. 25, 1930 

